Show a note for outdated / unsupported browsers

[noyainrain]

If we detect an outdated / unsupported browser, we should not start the app (and let it most likely randomly crash), but show a note to the user that they should update their browser.

We check for features we use of current/modern standards (and thus implicitly for support of previous standard releases):

• ES6:
  • Template strings
  • Promise
• HTML5:
  • Constraint validation
• DOM4:
  • classList
  • querySelector()

Check demo:

<script>
    // Use ES3 here, because there still are browsers out there that support no more recent version
    var syntax = true;
    try {
        eval("var x = `${1}`;");
        ...
    } catch (e) {
        syntax = false;
    }
    var outdatedBrowser = !(syntax && window.Promise && ...);
    if (outdatedBrowser) {
        document.write("<p>Please update your browser.</p>");
    }
</script>

[noyainrain]

Also show a warning if JavaScript/scripting is disabled (without Meetling won't run and we cannot check for browser compatibility) and ask the user to enable it.